Imaging systems are known, for example computed tomography systems (CT systems) which are adapted to irradiate a field of interest with radiation of an irradiation unit, like an X-ray tube which is moved relative to the field of interest along a first trajectory and along a second trajectory. First detection data and second detection data are acquired by a detection unit in dependence on the radiation after having passed the field of interest while the radiation source travels along the first and the second trajectory, respectively. The first and the second detection data are used to reconstruct an image of the field of interest. Such an imaging system is, for example, disclosed in “Exact and efficient cone-beam reconstruction algorithm for a short-scan circle combined with various lines” by F. Dennerlein et al., Medical Imaging 2005: Image Processing, edited by J. Michael Fitzpatrick, Joseph M. Reinhardt, Proceedings of the SPIE, Vol. 5747 (SPIE, Bellingham, Wash., 2005).
These known imaging systems have the disadvantage that the reconstruction process is limited by the run of the first and second trajectories. For example, if, after acquiring first and second detection data, the reconstruction process needs non-detected data which should have been acquired with the irradiation unit traveling along a certain trajectory, the acquisition has to be repeated in order to detect the missing data, so that the radiation dose applied to the field of interest, for example to a patient, increases. In order to overcome this drawback, the acquisition process, in particular the run of the first and the second trajectories, has to be planned carefully, which complicates the acquisition protocols of know imaging systems.